Directly printed panel having a two-layer design

ABSTRACT

A panel and a method for manufacturing of such a panel with a carrier plate, comprising a front side and a back side, and wherein the carrier plate comprises a layer system at least at the front side that is built from various polymer layers with different hardness values.

This application is a divisional of U.S. patent application Ser. No.14/900,231 filed Dec. 21, 2015, which is a National Phase ofInternational Application No. PCT/EP2013/062905 filed Jun. 20, 2013,which are both hereby incorporated herein by reference in theirentirety.

1. FIELD OF THE INVENTION

The present invention relates to a panel, particularly to a wall,ceiling, or floor panel with an improved surface primer as well as amethod for manufacturing it.

2. BACKGROUND OF THE INVENTION

A plurality of panels for wall, ceiling, and/or floor coatings are knownfrom the prior art. For example, so-called laminate panels are widelyspread as floor coating in the inner area. Laminate panels arerelatively cheap and can be well processed. Commonly, they are based ona carrier plate made of MDF or HDF material, on which a decor paper,impregnated with melamine resin, is applied to its upper side. Bygrouting under influence of heat and pressure, the resins cure, suchthat a highly abrasion-resistant surface is formed. To increase abrasionresistance, the surface is often provided with abrasion resistantparticles, in particular corundum, prior to grouting.

As an alternative to laminate panels, for some time past, high-qualitypanels based on PVC are known and are distributed as LVT (luxury vinyltiles). For example, a floor panel in the form of multi-layered,rectangular laminate with a carrier plate consisting of softpolyvinylchloride (PVC) is known from DE 10 2006 058 655 A1. Onto thesoft PVC layer, or plate respectively, a decor paper web is glued on,such that the visible surface of the PVC is applied with a decor. As analternative to such decor paper webs, applied to a PVC carrier plate,also the usage of plastic foils is known, which are also, for example,imprinted with a decorative decor.

From DE 10 2006 029 963 A1, a floor coating made of polyvinylchloride isknown, which is coated with a durable lacquer layer, to improvedurability of the PVC floor coating. The lacquer layer is based on anacrylate resin and is cured by means of radiation. The core of thisdocument relies in adding of electrical conductive substances to theresin, for proving the finished floor coating with antistatic and/orelectrical conductive properties.

More recently, LVT panels prevailed on the market that have a harder PVCplate with a thickness of 4-6 mm as a ground and on which a soft PVClayer is applied, comprising the features as described above. Specificprofiles are milled into the harder plate as coupling means. In such away, the single panels can easily be laid to form a plane area.

In a further development of the above described panels, so-called directimprinted panels have been developed. Commonly, for these directimprinted panels no more papers of foils are used, in particular nodecor paper. The decor layer is rather directly imprinted onto thesurface of the carrier plate, to which commonly a suitable pretreatmentis applied, by utilizing dispersion colors by means of an intaglioprinting process. In particular, before printing, a primer is applied bymeans of roller application. After drying of the decor layer, variousresin layers are applied and cured. The resin layers thereby serve as aprotective layer as well as abrasion resistant surface. To furtherimprove abrasion resistance, often abrasion resistant particles, likecorundum, are provided, too.

From WO 2007/042258, for example, a method for direct coating of woodmaterials is known, in which a thick protective layer made of plasticmaterial is applied liquidly onto the surface of a plate within onecoating step. The used plastic material is a liquid, polymerizableacrylate system that is cured by polymerization.

The mentioned prior art panels each have several pros and cons,depending from their structure, from the used manufacturing process, andfrom the used materials. For example, laminate panels can easily belaid, provide the opportunity to realize high-quality decors, and,additionally, are very durable. However, typically, the acousticproperties of laminate panels are disadvantageous, which produceannoying running noise when used as a floor coating. Responsible forthat is the very hard melamine layer on the laminate surface. Inaddition, this melamine layer is felt as cold and unpleasant. Coatingsbased on PVC have excellent acoustic properties and, additionally, havea pleasant haptic and feel relatively soft and warm, which is desirablein many cases, e.g. when used as a floor coating in a bathroom. However,for producing optical high-quality surfaces, such PVC floorings have tobe processed in a relative costly manner, and are thereforesignificantly more expensive compared to common laminate panels, atleast when they should provide comparable quality. A disadvantage of PVCpanels is that deep scratches can easily arise on the soft surface whenintensively used, which disturb the optical image. Furthermore, it isdisadvantageous that PVC floorings are not harmless from the ecologicalpoint of view. They comprise harmful plasticizers and chlorine is knownas very dangerous in case of fire (e.g. chlorine dioxin development).

Direct imprinted panels remove some of the disadvantages of laminatepanels and, e.g., need no decor paper soaked with melamine resin,whereby the manufacturing may be simplified. However, compared tolaminate panels, they have similar disadvantages with regard to acousticproperties and haptic.

In light of these known panels, or respectively coatings, the objectiveof the present invention is to provide a panel, particularly a wallpanel, a ceiling panel, or a floor panel, comprising as much as possibleof the different advantages of the known panels, but at the same time,however, minimizing the existing disadvantages of the various panels. Inaddition, the further objective is to manufacture such a panel in acheap and relatively simple manner. A further objective is providingsuch panels that have a good durability and which allow to realizehigh-quality decorative patterns.

This and other objectives, which will be mentioned in the presentdescription or that will become apparent for the skilled person, areachieved by a panel according to claim 1 and with a respectivemanufacturing method of such a panel according to claim 24.

3. DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a panel, like a wall, ceiling, butparticularly a floor panel is provided that comprises a carrier platewith a front side and a back side, wherein at least a layer system isapplied at the front side. The front side shall be understood as theside which is the used side that points to the observer, when the panelis laid, e.g., in form of a floor. The carrier plates can optionally bedivided into panels. At their side edges, the panels can providecoupling means, particularly in form of tongue and groove elements, asknown from the area of floor laminate panels. Particularly suited tongueand groove elements allow connecting various similar panels in paralleldirection to the front side and also perpendicular to the front side byform fitting. Of course, the process sequence can be applied to thepanels one by one, wherein this approach is less economical. The layersystem, according to the invention, originating of the front side,comprises a first elastic layer made of a polymer and which is calledlayer S1 in the following. This first polymer layer according to theinvention having a thickness of 20-600 μm and a Martens hardness M_(S1)of 0.5-120 N/mm², preferably between 2 and 50 N/mm², more preferablybetween 2 and 40 N/mm², and most preferably between 2 and 30 N/mm², andit is soft elastic. Above this first elastic layer, a second layer S2 isprovided that has a thickness of only 10-200 μm and a Martens hardnessM_(S2) which is greater than the Martens hardness of the first elasticlayer, i.e. M_(S2)>M_(S1). The Martens hardness M_(S2), determined atthe panel surface, is between 5-300 N/mm², preferably at 15-150 N/mm²,more preferably between 20 and 100 N/mm², and most preferably between 25and 90 N/mm².

The structure of the layer system of the panel according to theinvention implicates that the surface of a coated panel in such away—independent from the material of the carrier plate—feels relativelysoft and has for human feelings a comfortable warm haptic impression. Inparticular, providing a thick elastic layer S1 has significant acousticadvantages. Compared to a laminate reference floor, the layer systemaccording to the invention leads to a significant noise damping effectwhen walked on. According to IHD-W 431, a loudness of 26 Sone isdetermined for a laminate reference floor. The floor, provided with anelastic layer S1 and a layer S2 comprises an improvement of 10-70%compared to this reference floor. A PVC (LBT) floor was measured with animprovement of 40% compared to the reference.

A plurality of different materials is possible as materials for thecarrier plate since the relevant physical properties of the panelaccording to the invention are substantially determined by the appliedlayer system. Thus, generally, the carrier plate of the panel accordingto the invention is preferred with a MDF plate, an HDF plate, a PVCplate, a cement fiber plate, a WPC plate (wood powder composite), athermoplastic recycling plate, a wood plate, a wood veneer plate, or aparquet plate like a pre-fabricated parquet plate. As mentioned at thebeginning, the carrier plate may comprise coupling means in form oftongue and groove elements at its sides, such that the panels accordingto the invention can, for example, be easily laid to form a covering ona floor.

In general, materials for the layers S1 and S2 (and S3) are preferablybased on acrylate systems or based on acrylates, respectively. Anacrylate system is herein to be understood as a polymerizable mixture ofmono-, bi- and multi-functional acryl acid based compounds comprisingdouble bonds. Typical representatives are, for example,dipropylenglycoldiacrylate, 1,6-hexandioldiacrylate, polyurethaneacrylate acid ester, polyester-acrylate acid ester as available on themarket according to the production program of the company BASF under thetrademark Laromer™ types.

Layer S1 is preferably a polymer based on a radical polymerizableoligomer and/or oligomer mixture. Preferably, it is based on radiationhardenable acrylate oligomers (acrylate system). The oligomers arechosen such that the layer provides damping properties, characterized inthat the Martens hardness is preferably 0.5-120 N/mm², more preferably2-50 N/mm². Such an oligomer formulation consists, for example, of oneor more unsaturated acrylates that comprise a polyester, polyetherand/or a polyurethane structure, with a functionality of 1-4, preferably<2. Commercially available examples are the Laromer PO 43 F, the LaromerUA 9033 or the Laromer UA 19 T of BASF. Additionally, the oligomermixture may comprise low viscose acrylate ester with a functionality of1-4, preferably with a functionality of 1-2. Commercially availableexamples are the Laromer LR 8887, Laromer DPGDA, Laromer TPGDA of BASF.For hardening by means of UV-radiation, photo initiators like mono- orbi-sacylphosphinoxide, alphahydroxycetone, benzophenon derivate,benzildimethycetal or phenylglyoxalate are needed. In addition, theformulation can comprise additives like wetting agents, defoamers,inorganic or organic filling materials. As additives, for example, polyacrylate, silicones, talcum, barium sulfate, chalk, silicic acid orpolyuria derivates may be used.

The material of the second layer S2 is preferably based on a radicalpolymerizable acrylate oligomer (acrylate system) or a radicalpolymerizable acrylate mixture, consisting of one or more unsaturatedacrylates (acrylate system), a polyester, polyether and/or polyurethanestructure with a functionality of 1-8, preferably 3-6. Examples are theLaromer PE 9074, Laromer 8863 or Laromer LR 8987 as raw lacquermaterials of BASF. Preferably, these acrylate mixtures further compriselow viscose acrylate ester with a functionality of 1-6, preferably witha functionality of 2-4. For example, following raw materials of BASFwith the trademark name Laromer HDDA, Laromer TMPTA, Laromer PPTTA canbe used. In case of UV-linked systems, photo initiators as for examplemono or bisecylphosphinoxide, alphahydroxycetone, benzophenon derivate,benzildimethylcetal or phenylglyoxylate are applied. Furthermore,additives like wetting agents, defoamers, matting agents and inorganicor organic filling materials may be applied, like poly acrylate,silicones, talcum, barium sulfate, chalk, silicic acid or polyuriaderivates. The oligomers are chosen such that the surface hardness liesin the above-mentioned ranges. Furthermore, the raw material selectionis made such that the layer S2 has, besides damping properties, inparticular, a high abrasion resistance (scratch resistance, microscratch resistance, abrasion resistance). The skilled person knows thatthese properties are achieved by network density and modifications, forexample, with nano particles.

Preferably, the thickness of the carrier plate is between 3 and 20 mm,more preferably between 4 and 15 mm and even more preferably between 3and 12 mm, and most preferably between 4 and 10 mm. Depending on theusage and the applied decor (if available), different shapes arepossible. If, for example, the panel shall imitate a real wood decor andbe laid as a floor panel or wall panel, a square base form of thecarrier plate or the panel is advantageous, e.g. in a square shape of1.5-2 m in length and 10-30 cm in width.

As mentioned at the beginning, the relevant physical properties of thesurface of the panels according to the invention are substantiallydetermined by the layer system according to the invention. The thickfirst elastic layer S1 is decisive for the acoustic properties of thepanels. Basically, preferred hardness values according to Martens forthe layer S1 are between, as mentioned above, 0.5-120 N/mm², morepreferably between 2-50 N/mm², even more preferably between 2-40 N/mm²and most preferably between 2-30 N/mm². In every case, the second layerS2 must have a greater hardness compared to the first layer and shouldbe, as mentioned above, in a range between 5-300 N/mm², more preferablyat 15-150 N/mm² and more preferably between 20-100 N/mm² and mostpreferably between 25-90 N/mm². The skilled person knows that even ifthe mentioned ranges for the preferred hardness of M_(S1) and M_(S2)partially overlap, it is substantially in the focus that M_(S2) isgreater than Msi.

Determining the Martens hardness is known by the skilled person. Duringdevelopment of the present invention a Taber Abraser measurement device5151 of Taber Industries was used. Every 200 rounds with an abrasivepaper S41 the hardness and the track depth was determined of the probes.Determination of the Martens hardness (registered hardness control undertest force influence) was conducted according to DIN EN ISO 14577. As ameasurement device, a “Fischerscope H100” of the Helmut Fischer GmbH wasused. Following test parameters have been used: maximum force: 50/30 mNand measurement duration: 20 seconds. The determination of the trackdepth has been conducted with a mechanical touch cut measurement device.As a measurement device a perthometer S3P of the company Perthen wasused.

During surveying the probes, it has been shown that probably due to therelatively soft used materials more or less large deviations in thehardness of a given layer depth occur. Thus, it is necessary to measureat various points to achieve meaningful representative data bycalculating average values. During the conducted measurements, thehardness and the track depth have been each measured at four locations,after 200 rounds of the abrasive paper. It appears, in most cases thatfour measurement points provide sufficient accuracy. Of course, evenmore precise measurement results will be achieved when more than fourmeasurement points are used, e.g. eight.

Preferably, the thickness of the elastic layer S1 is in range of 20-600μm, more preferably of 40-500 μm, even more preferably of 80-450 μm, andmost preferably of 120-240 μm. The second layer S2 has, independently ofthe thickness of the first layer, preferably a thickness of 10-180 μm,more preferably of 20-100 μm and most preferably of 30-80 μm. Thereby,it is apparent for the skilled person, the thicker the first elasticlayer S1 is chosen, the more elastic the properties of the surface ofsuch coated panels are. The layer S1 is preferably applied one afteranother in part steps, particularly by means of various roller deviceswith respective gelling after the roller application devices. Gelling isunderstood that in the respective layer a radical polymerization isinitiated by radiation, e.g. by means of UV, but this polymerization iscancelled fast, such that the adhesion of the following layers isensured. In other words, the part layers are each not completely cured,but only in part. In this way, among other things, also the adhesion ofthe part layers to each other is increased. The layer S1 can,alternatively, be applied in one single step.

Preferably, a further decor layer is applied between the front side andthe layer S1, comprising a printing ink (ink) or consists of thisprinting ink, respectively. The term “printing ink” is herein usedgenerically and shall not denote a single color, but printing ink in ageneric fashion: with regard to digital four-color printing, theprinting ink, for example, consists of four different colors (cyan,magenta, yellow, black), of which the printing image is generated byspraying on ink drops. When using indirect intaglio printing, the decorimage, as is known, is generated by means of rotating printingcylinders. By means of the printing cylinders, decor specific mixturecolors are applied. In principle, with respect to the present invention,it is preferred that the layers S1 and S2 are substantially transparentsuch that they can serve as protection for an underlying decor layer.

Commonly, dispersion colors are used as printing ink in the prior art,in particular acrylate colors. These dispersion colors are regularlyutilized by the commonly used intaglio printing process. Dispersioncolors are printing inks that normally consist of three main components,namely a) a dissolver (commonly water), b) a bonding agent in form ofplastic polymers that are stored together and form a solid layer whenthe solvent evaporates, and c) color pigments for generating the desiredcover and the desired color tone. The hardening of these dispersioncolors is not performed by means of polymerization, but by evaporationof the solvent, since the bonding agents already exist in terms ofpolymers. The polymers included in the dispersion connect themselves bymeans of evaporation of the bonding agents in a purely physical mannerand form a solid, closed layer.

Surprisingly, it has been found out in connection with the presentinvention that improved adhesion properties of the layer systemsaccording to the invention can be achieved, when, in the present case,instead of usual dispersion colors, polymerizable printing inks areused. The positive effect is particularly remarkable when the printingink of the decor layer and at least in part of the first elastic layerS1 are cured or polymerized together, respectively (when the decor layeris directly imprinted, as e.g. with digital printing, the decor layerconsists of the printing ink, so to speak). Curing or partially curing(gelling) of a polymer layer or a polymerizable printing ink is to beunderstood as a chemical reaction in which a polymerization takes place.This has to be distinguished from drying of such layers, wherein onlythe solvent, like the water content of a dispersion color, evaporates oris reduced in a purely physical manner. By means of the combined(partial) curing of the polymerizable printing ink and the materials forthe first elastic layer, probably a chemical linking occurs that theborder surface of both layers, of which it is assumed that it isresponsible for the improved adhesion of the layers. The commonly useddispersion colors do not comprise polymerizable acrylate systems suchthat no chemical linking between the printing ink, i.e. the decor layer,and the elastic layer takes place.

Generally, the printing inks used for the present invention aretherefore preferably polymerizable printing inks and in particularpolymerizable acrylate systems. Polymerizable printing inks comprise asmain component bonding agents, namely reactive double bondingscontaining resins; monomers or oligomers, like acrylate monomers andacrylate oligomers; optionally photo initiators for radiation hardenableprinting inks; additives like defoamers, flow additives and the like;and color pigments and filling material for achieving specific physicaltechnical properties. Generally, the used printing inks for the presentinvention are preferably radiation hardenable, particularly by UV rayhardenable printing inks. More preferably, the printing ink is based ona polymerizable acrylate and/or N-vinylcaprolactam.

In a further embodiment according to the invention, a third elasticlayer S3 is provided on the front side beneath the decor layer which hasa Martens hardness M_(S3), wherein the hardness of the third elasticlayer is preferably equal or less than the hardness of the first elasticlayer S1, i.e. M_(S3)≤M_(S1). In this way, particularly thick layersystems with corresponding good elastic properties may be generated.Preferably, the layer S3 should have a thickness of 10-300 μm, morepreferably of 30-150 μm and most preferably of 60-120 μm. For the layerS3, a radical polymerizable acrylate mixture is used, as it is providedfor the layer S1 and described above. This oligomer mixture ispreferably applied with pigments before application in order to providethe layer with a covering color as printing ground, i.e. that this layerS3 should preferably not be transparent in order to achieve a sufficientprinting quality. The decor layer, including possible necessary primersand primary coatings, is then applied onto the before applied layer S3.The advantage of this third layer S3 is that the total layer system canbe designed very thick without impacting the optical impression of aneventually present decor layer since only the first elastic layer S1 andthe second layer S2 lie between the observer and the decor layer.

The layer system according to the invention has the advantage that nofurther paper or plastic foils are necessary at the front side of thepanel or the carrier plate, as it has been necessary in manyapplications in the prior art. Therefore, the panels can be applied witha layer while running through a machine and do not have to be stucktogether with a before produced paper or plastic foil.

In a further embodiment according to the invention, the decor layer,including the possibly necessary support layers like primers or coatingprimers can be arranged between layer S1 and the wear layer S2.

In addition, the present invention also relates to a process formanufacturing a panel, particularly a panel as discussed above. In thisprocess, a carrier plate, like a MDF or HDF carrier plate, is providedin a first step. The carrier plate is applied with a layer of liquidradiation hardenable acrylate such that is selected that aftersuccessfully curing, it provides a Martens value M_(S1) of 0.5-120N/mm². With common roller application processes normally layerthicknesses of up to 80 μm, and in special cases up to 100 μm can beapplied in one working step. In order to achieve the desired layerthicknesses for the first elastic layer S1, it will be commonlynecessary to harden each applied layer, preferably by means of radiationin order to apply a further layer on this partly or completely curedlayer. Since preferably always the same materials are used, a homogenouselastic—according to the hardness—layer S1 with a thickness of up to 600μm can be generated. However, for each of the layers of layer S1,different materials with different values for M_(S1) can be used, which,however, should preferably not differ too much from each other andshould in every case be in the range according to the invention of0.5-120 N/mm². Particularly, an as much as possible homogeneous hardnessin the final layer S1 (or S2) is preferred, which can most easily beachieved by using the same or at least similar materials. Afterachieving the desired final thickness of the elastic layer S1, after S1has been partially or completely cured, a layer with further liquidradiation curable acrylates is applied, wherein this is chosen such thatthe layer comprises a Martens hardness M_(S2) after curing, which isgreater than the Martens hardness of the before applied first elasticlayer. Also in this case, it might be necessary to apply various layerswith respective connected (part-) curing steps, if a particularly largefinal thickness of the second layer S2 is desired. Although in this casedifferent materials can be used for every layer of the layer S2 withdifferent values for M_(S2), as long as (every) M_(S1) is less than thesmallest M_(S2) of the single layers of the layer S2. However, also hereit is preferred to use the same or at least similar materials for thepartial layers of the layer S2, since this improves the cohesion of thepartial layers and may lead to an increased durability of the totallayer S2 (respectively S1).

Advantageously, before applying the first elastic layer S1 onto thesurface of the carrier plate, a primer is applied and a decor layer isimprinted thereon. Preferably, this is done by direct printing, whereinthe above in connection with the panel according to the inventiondescribed technical information are also basically usable for thepresent method. In other words, the decor layer or the decorativepattern is here also preferably applied by means of a polymerizableprinting ink and more preferably at least a first layer of the firstelastic layer S1 is applied onto the not yet (at least not completely)cured printing ink and then cured together with the printing ink. Inthis manner, a particularly good connection of the layer system with thesurface of the carrier plate is achieved.

EXAMPLE 1

In a first step, an HDF carrier plate with a thickness of 8 mm isapplied with a primer based on a commercial watery acrylate dispersionwith an application of 10 g/m² by means of a roller application device.In a next step, smoothing of the plate by means of a roller applicationdevice by means of a filler based on a highly filled watery acrylatedispersion with an application amount of 25 g/m² is done. Afterwards, aprinting ground (primer coating) based on a watery acrylate dispersionenriched with filling materials and color pigments is applied by meansof a molding process (i.e. by a curtain coating process) with an amountof 70 g/m². After each of these coating steps, an intermediate drying ata temperature between 80-200° C. is performed. The plates treated insuch a way are then applied to a printing machine, substantiallyconsisting of a gravure roller and a rubber roller used for transferringthe printing image from the gravure cylinder onto the plate. Theprinting image is generated by means of three down-streamed printingdevices, wherein by means of each of the printing devices an owndispersion printing ink, consisting of color pigments and a wateryacrylate dispersion is applied. For an imitation of a dark nut treewood, for example, 5 g/m² of printing ink are applied. In a furtherprocess, a commercial UV primer is applied onto the printing color layerby means of a roller application device. By means of a subsequent rollerapplication device, a radical polymerizable acrylate oligomer mixture(1) is applied in an amount of 80 g/m². This oligomer mixture (1)comprises 70 parts of Laromer PE 9032 and 25 parts of Laromer TBCH ofBASF, as well as five parts of further additions (benzildimethylcetal asa photo initiator, an aliphatic urethane acrylate with a functionalityof 3). By means of a UV emitter, gelling (partially curing) is performedfor this layer. By means of a further roller application device, againthe same (or alternatively a similar) oligomer mixture (1) in the amountof 80 g/m² is applied and at least in part cured. Onto the in such a waybuilt first elastic layer S1 a layer S2 with a further double bondingcontaining, with photo initiators enriched radiation hardenable oligomer(2) in an amount of 50 g/m² is applied by means of a third rollerapplication device and is polymerized by means of UV radiation. Thisoligomer (2) consists of a mixture of 75 parts of Laromer PE 9074, 20parts Laromer HDDA of BASF and 5% of further additives (among otherthings phenylglyoxalate as photo initiator) and has a greater hardness(M_(S2)) compared to the first layer S1.

EXAMPLE 2

Panels for which the printing image is generated by means of radiationhardened printing inks.

Again, it is used an 8 mm thick HDF carrier plate and, according toexample 1, it is provided with a watery primer, filler and printingground. On the plate, treated in such a way, the same decor imageaccording to example 1 is generated by means of a digital printer.However, hereby no dispersion colors are used, but UV radiationhardenable digital printing inks. For generating the printing image, anamount of about 2 g/m² of ink is needed. At first, the ink is fixed with150 mJ/cm² (mercury) and then, the first layer of layer S1 according tothe first example is applied and together with the printing ink cured atleast in part (gelled). The further steps are then performed accordingto example 1.

EXAMPLE 3

An HDF carrier plate undergoes the production steps up to behind theprinting machine according to example 1. Onto the dried printing ink, acommercial watery UV primer is applied. By means of the precedingprocess, the plate is heated up to a surface temperature of 50-60° C.,such that water of the primer evaporates fast such that the primer isfixed. Subsequently, an oligomer mixture (1) according to example 1 isapplied in an amount of 50 g/m² by means of a roller device and gelledby means of UV radiation. Afterwards, a second roller application of 50g/m² of that oligomer mixture (1) (or a similar one) with a subsequentgelling and, finally, a third application (1) of 50 g/m² with subsequentgelling in order to form the layer S1. Then, by means of a rollerapplication device, the wear or covering layer (i.e. layer S2) of 30g/m² is applied and hardened by means of UV radiation. The oligomer (2′)for the covering layer S2 consists of a mixture of 75 parts Laromer PE9074, 20 parts Laromer HDDA of BASF and 5% of further additives (amongothers, phenylglyoxalat as photo initiator and a matting agent). Bymeans of the amount of the added matting agent, the desired degree ofgloss of the surface is controlled. The further processing of the platesinto floor panels is preformed according to example 1.

EXAMPLE 4

In a first step, an HDF carrier plate with a thickness of 8 mm isapplied with a primer based on a commercial watery acrylate dispersionwith an application of 10 g/m² by means of a roller application device.In a next step, smoothing of the plate by means of a roller applicationdevice by means of a filler based on a highly filled watery acrylatedispersion with an application amount of 25 g/m² is performed.Subsequently, a UV radiation hardenable mass in an amount of 40 g/m² isapplied by means of a roller device. This radiation hardenable massconsists of 65 parts of the oligomer mixture (1) according to example 1and of 35% finest dispersed titanium dioxide. Subsequently, it is gelledby means of UV radiation. A second application of 40 g/m² of this massis performed by means of a down-streamed roller application device withsubsequent gelling. The resulting layer is in accordance with theabove-described layer S3. Afterwards, digital printing according toexample 2 is conducted. Furthermore, optionally, a commercial UV primerin an amount of 3 g/m² is applied by means of a roller applicationdevice. The further coating with the oligomers (1) and (2) used forgenerating the layers S1 and S2 is performed according to example 1 andalso the manufacturing of the panels of the base plates.

Subsequently, some determined properties of the manufactured floormaterials according to the examples 1-4 are presented:

-   -   a) Determining the walking noise emission according to IHD-W 431        (version of May 14, 2012)

The characteristic values have been determined with non-compliance ofthe spectrums with the biggest and smallest noise unit (outliercorrection according to IHD-W 431). The result is shown in terms of adifference between the A-rated total sound pressure level and the noiseunit of the examined variance compared to the reference floor. Thechanging of the linear parameter noise unit (N) is determined accordingto the reference in percent as follows:

Change in percentage:((Nref−Nf)*100%)/Nref

The determined characteristic value shows the increase (negative value)or decrease (positive value) in percent of the loudness experience. Thereference is a common laminate floor with a melamine resin coating and aplate thickness of 8 mm.

TABLE 1 A-rated total sound pressure level Reference Probe (mid-range(mid-range Improvement spectrum) spectrum) extent Version [dBA (A)] [dBA(A)] [dBA (A)] Example 1 75.3 64.8 10.5 Example 2 75.3 65.2 10.1 Example3 75.3 65.5 9.8 Example 4 75.3 64.3 11.0 LVT (PVC) floor 75.3 64.9 10.4(5 mm in thickness)

The examples show that a significant noise reduction during walking canbe achieved by means of the coating according to the invention. Areduction of 10 dB is felt like a halving of the loudness by means ofthe human hearing. To have a direct comparability, only HDF carrierplates have been used as carrier plates in the examples 1-4. Withalternative carrier plates further significant noise reductions arepossible.

4. DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, the present invention is explained in more detail withreference to the attached figures. At this:

FIGS. 1a and b show an exemplary layer structure of a schematicillustration; and

FIG. 2 shows an exemplary system for manufacturing of the panelaccording to the invention in a schematic view.

In FIG. 1a , a schematic layer structure of a panel 10 according to theinvention is shown. The illustration is purely schematic and not true toscale. In particular, the carrier plate 11 is significantly thickercompared to the further layers 12-18, which lie in a range of somehundred μm. Furthermore, the single layers are shown in an explosionview in order to simplify the understanding and are in a real casedirectly adjacent to each other or directly arranged above each other.In the shown example, a carrier plate 11 with a thickness of about 8 mmmade of an HDF material is shown. At the backside of the carrier plate11 a moisture barrier 13 in form of an appropriate plastic foil ispasted. The moisture barrier is optional and depending on the materialof the carrier plate 11 and the desired usage area. A carrier plate 11furthermore comprises coupling means in form of tongue 15 and grooveelements 14, which are only shown schematically in FIGS. 1a (and b).Suitable coupling means in form of tongue and groove elements that allowconnecting various similar panels in parallel direction of the frontside and also perpendicular to the front side by means of form fittingare known by the skilled person. Commonly, at the four sides of a squareor quadrangle carrier plate opposing complementary coupling means areprovided. Details about such coupling means or locking profiles areknown by the skilled person from the technology of laminate floorproduction, as e.g. known from the document WO 0188306 or from thedocument WO 0148332 of the same applicant, which are hereby entirelyincorporated by reference.

In the shown layer system of panel 10, a primer coating 16 with athickness of, for example, 50-200 μm is provided which is based on awatery acrylate system. Beneath the primer, further very thin primercoatings and/or filler layers may be applied as known by the skilledperson from the area of direct imprinted panels. A decor layer or adecor 18 is imprinted onto the primer 16. The decor 18 or the decorlayer 18 have been applied, for example, by means of a polymerizableprinting ink by a digital four color printing. A first elastic layer S1is located above the decor layer 18 with a thickness of 200 μm and aMartens hardness M_(S1) of 15 N/mm². A second layer S2 is applied ontothe first elastic layer S1, which has a thickness of 80 μm and a Martenshardness of about 25 N/mm².

The example of FIG. 1b corresponds to the example of FIG. 1a with thedifference that a further elastic layer S3 is provided between theprimer coating 16 and the decor layer 18. The layer S3 has preferably aMartens hardness Mss which is less or equal than the Martens hardness ofthe layer S1, therefore M_(S3)≤M_(S1). In the example of FIG. 1b , thefirst layer S1 may be provided in a slightly thinner way compared to theexample of FIG. 1a which is shown in both figures schematically by meansof different thicknesses.

In the following, the manufacturing of a panel according to theinvention is exemplarily shown in FIG. 2. FIG. 2 shows in a schematicway a coating system for coating carrier plates 11. The carrier platesare trimmed and profiled after the coating in a separate profiling line(not shown). For example, the carrier plates 11 have a thickness between3-20 mm, a length (in transport direction of the system of FIG. 2) of150-200 cm and a width of 125-210 cm. However, any other platedimensions can be used for the carrier plates, which are cut in thedesired form and size at the end of the process. The stations shown inFIG. 2 of the system are not to be understood conclusive, but only serveas an example explanation of the methods according to the invention. Infront, behind and between the shown stations, further processingstations may be provided, like drying stations, stations for applyingprimers, stations for applying filler, control and monitor devices etc.The carrier plates 11 are, for example, transported through the coatingsystem by means of roller conveying device 20.

In the first shown station 30, a grounding mass is applied onto thefront side (main side) of the carrier plates 11 by means of a liquidcurtain 31 of coating material. The liquid curtain 31 ranges among thecomplete width of the plate and the plates are transported through thiscurtain and are coated at the same time. Below the device 30 foroutputting the curtain, a collection container 32 is located, in whichthe liquid curtain drops, when no plate is passed through the curtain,as for example, at a gap between two consecutive plates. Preferably, awatery acrylate dispersion is used as a coating material for thegrounding. In a subsequently arranged drying station 40, the appliedgrounding is dried by means of hot air, i.e. water is extracted from thewatery acrylate dispersion. After drying the grounding, a decor layer isimprinted onto the grounding by means of a digital printing device 45.This decor layer, for example, can imitate real wood, but nowadayscommercial digital printing works are able to nearly print every desireddecor or pattern on the plates. Preferably, a printing ink is utilizedin printing device 45 that is polymerizable by means of radiation, i.e.a printing ink that is based on a polymerizable acrylate and/orN-vinylcaprolactam. It is apparent for the skilled person that theillustration of the digital printing device 45 is only purely schematicand that such printing devices commonly consist of several stations.After imprinting the desired decor, a first coating device 50 applies afirst layer of liquid radiation hardenable aliphatic acrylate. Thematerial is chosen in such a way that it comprises a Martens hardnessM_(S1) of 0.5-120 N/mm² after the curing. The device 50 is a rollerapplication device and is able to apply a layer thickness of about40-100 μm in one process step. In the subsequent station 60, the appliedlayer of liquid radiation hardenable aliphatic acrylate is cured atleast in part by means of UV radiation. Subsequently, a second device50′ follows in order to apply a second layer of the same liquidradiation hardenable acrylate compared to the first layer. Also here,the station 50′ is a roller application station which is commonly ableto apply layer thicknesses of 30-100 μm. In station 60′ this secondlayer is at least cured in part by UV radiation. Subsequently, in athird coating device 50″ a third layer of the same liquid radiationhardenable acrylate is applied and in the third radiation station 60″ itis at least in part cured by means of UV radiation. In the schematicview of FIG. 2 three such devices are thus shown, which are able toapply three layers in one layer, but however, also more or less devicesmay be available, depending on the desired total thickness of the firstelastic layer S1. In any case, there is a first elastic layer S1available at the exit of the last radiation station 60″ with a thicknessof about 150 μm. Then, onto this first elastic layer S1, a layer ofliquid radiation hardenable acrylate is applied in an applicationstation 70 that is chosen in a way such that after the curing itcomprises a Martens hardness M_(S2) that is greater than the Martenshardness of the first elastic layer and preferably at 5-300 N/mm². Here,in FIG. 2, as an example, only an application device 70 and a station 71for radiation hardening is shown, but however, also for the second layerS2 various devices may be provided, depending on the desired finalthickness of the layer of S2. Then at the exit of the coating device, acoated panel, according to the invention will be available, that may befurther processed as desired.

What is claimed:
 1. A panel comprising a carrier plate having a frontside and a back side, wherein the carrier plate has a layer system atleast at the front side, and the carrier plate comprises tongue andgroove elements at its sides, enabling coupling of various similarpanels in parallel direction to the front side and perpendicular to thefront side by form fitting, wherein the layer system, originating of thefront side, comprises: a first elastic layer S1 made of an polymer,having a thickness of 20 to 600 μm and a Martens hardness M_(S1) of 0.5to 120 N/mm²; a second layer S2 made of a polymer, having a thickness of10 to 180 μm and a Martens hardness M_(S2), wherein M_(S2)>M_(S1); and adecor layer arranged between the front side and the layer S1, comprisinga printing ink; the printing ink is based on a polymerizable acrylateand/or N-vinylcaprolactam.
 2. The panel according to claim 1, whereinthe polymer of the layer S1 is an aliphatic polymer.
 3. The panelaccording to claim 1, wherein M_(S1) is between 2 and 50 N/mm².
 4. Thepanel according to claim 1, wherein M_(S2) is between 50 and 300 N/mm².5. The panel according to claim 1, wherein the first elastic layer S1has a thickness of 40 to 500 μm.
 6. The panel according to claim 1,wherein the second elastic layer S2 has a thickness of 10 to 180 μm. 7.The panel according to claim 1, wherein the polymer of the layer S1 isbased on a radiation hardened aliphatic acrylate.
 8. The panel accordingto claim 1, wherein a third elastic layer S3 is arranged between thefront side and decor layer, having a Martens hardness M_(S3), whereinM_(S3)≤M_(S1).
 9. The panel according to claim 8, wherein the layer S3has a thickness of 10 to 300 μm.
 10. The panel according to claim 1,wherein the printing ink of the decor layer and at least a part of thelayer S1 have been hardened together.
 11. The panel according to claim1, wherein the decor layer has been applied by digital printing.
 12. Thepanel according to claim 1, wherein the polymer of the layer S2 is basedon one or more of the following acrylates: 1,6-hexandioldiacrylate,polyester acrylate, polyurethane acryl acid ester or dipropylene glycolediacrylate.
 13. The panel according to claim 1, wherein the carrierplate has a thickness between 3 and 20 mm.
 14. The panel according toclaim 1, wherein the carrier plate is a MDF plate, a HDF plate, a PVCplate, a cement fiber plate, a WPC plate (wood powder composite), athermoplastic recycling plate, wood plate, a wood veneer plate, or aparquet plate.
 15. The panel according to claim 1, wherein no paper orplastic foil is applied to the front side of the panel.
 16. The panelaccording to claim 8, wherein the source materials of the layers S1, S2,and S3 are radiation hardenable materials.
 17. The panel according toclaim 1, wherein the layers S1 and S2 are transparent.
 18. The panelaccording to claim 1, wherein the panel is not provided withabrasion-resistant particles.
 19. The panel according to claim 1,wherein the layer system has a damping effect of at least 5 dB, comparedto the uncoated carrier plate, measured according to EPLF norm.
 20. Thepanel according to claim 1, wherein the hardness of the elastic layer S1is substantially constant over the total thickness, and in that thehardness differences within the layer are less than 20 N/mm².
 21. Thepanel according to claim 1, wherein the panel is a wall panel, ceilingpanel, or floor panel.
 22. The panel according to claim 1, whereinM_(S1) is between 2 and 40 N/mm².
 23. The panel according to claim 1,wherein M_(S2) is between 15 and 150 N/mm².
 24. The panel according toclaim 1, wherein the first elastic layer S1 has a thickness of 80 to 450μm.
 25. The panel according to claim 1, wherein the second elastic layerS2 has a thickness of 20 to 100 μm.
 26. The panel according to claim 1,wherein the polymer of the layer S1 is based on a radiation hardenedaliphatic urethane acrylate.
 27. The panel according to claim 1, whereinthe printing ink of the decor layer and at least a part of the layer S1have been hardened together by radiation.